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<li class="toctree-l2 current"><a class="current reference internal" href="#">RBD 增量备份</a><ul>
<li class="toctree-l3"><a class="reference internal" href="#header">Header</a></li>
<li class="toctree-l3"><a class="reference internal" href="#metadata-records">Metadata records</a><ul>
<li class="toctree-l4"><a class="reference internal" href="#from-snap">From snap</a></li>
<li class="toctree-l4"><a class="reference internal" href="#to-snap">To snap</a></li>
<li class="toctree-l4"><a class="reference internal" href="#size">Size</a></li>
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<li class="toctree-l3"><a class="reference internal" href="#data-records">Data Records</a><ul>
<li class="toctree-l4"><a class="reference internal" href="#updated-data">Updated data</a></li>
<li class="toctree-l4"><a class="reference internal" href="#zero-data">Zero data</a></li>
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<li class="toctree-l3"><a class="reference internal" href="#final-record">Final Record</a><ul>
<li class="toctree-l4"><a class="reference internal" href="#end">End</a></li>
</ul>
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<li class="toctree-l3"><a class="reference internal" href="#id1">Header</a></li>
<li class="toctree-l3"><a class="reference internal" href="#id2">Metadata records</a><ul>
<li class="toctree-l4"><a class="reference internal" href="#id3">From snap</a></li>
<li class="toctree-l4"><a class="reference internal" href="#id4">To snap</a></li>
<li class="toctree-l4"><a class="reference internal" href="#id5">Size</a></li>
</ul>
</li>
<li class="toctree-l3"><a class="reference internal" href="#id6">Data Records</a><ul>
<li class="toctree-l4"><a class="reference internal" href="#id7">Updated data</a></li>
<li class="toctree-l4"><a class="reference internal" href="#id8">Zero data</a></li>
</ul>
</li>
<li class="toctree-l3"><a class="reference internal" href="#id9">Final Record</a><ul>
<li class="toctree-l4"><a class="reference internal" href="#id10">End</a></li>
</ul>
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<div id="dev-warning" class="admonition note">
  <p class="first admonition-title">Notice</p>
  <p class="last">This document is for a development version of Ceph.</p>
</div>
  <div id="docubetter" align="right" style="padding: 5px; font-weight: bold;">
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  <section id="rbd">
<h1>RBD 增量备份<a class="headerlink" href="#rbd" title="Permalink to this heading"></a></h1>
<p>This is a simple streaming file format for representing a diff between
two snapshots (or a snapshot and the head) of an RBD image.</p>
<section id="header">
<h2>Header<a class="headerlink" href="#header" title="Permalink to this heading"></a></h2>
<p>“rbd diff v1\n”</p>
</section>
<section id="metadata-records">
<h2>Metadata records<a class="headerlink" href="#metadata-records" title="Permalink to this heading"></a></h2>
<p>Every record has a one byte “tag” that identifies the record type,
followed by some other data.</p>
<p>Metadata records come in the first part of the image.  Order is not
important, as long as all the metadata records come before the data
records.</p>
<section id="from-snap">
<h3>From snap<a class="headerlink" href="#from-snap" title="Permalink to this heading"></a></h3>
<ul class="simple">
<li><p>u8: ‘f’</p></li>
<li><p>le32: snap name length</p></li>
<li><p>snap name</p></li>
</ul>
</section>
<section id="to-snap">
<h3>To snap<a class="headerlink" href="#to-snap" title="Permalink to this heading"></a></h3>
<ul class="simple">
<li><p>u8: ‘t’</p></li>
<li><p>le32: snap name length</p></li>
<li><p>snap name</p></li>
</ul>
</section>
<section id="size">
<h3>Size<a class="headerlink" href="#size" title="Permalink to this heading"></a></h3>
<ul class="simple">
<li><p>u8: ‘s’</p></li>
<li><p>le64: (ending) image size</p></li>
</ul>
</section>
</section>
<section id="data-records">
<h2>Data Records<a class="headerlink" href="#data-records" title="Permalink to this heading"></a></h2>
<p>These records come in the second part of the sequence.</p>
<section id="updated-data">
<h3>Updated data<a class="headerlink" href="#updated-data" title="Permalink to this heading"></a></h3>
<ul class="simple">
<li><p>u8: ‘w’</p></li>
<li><p>le64: offset</p></li>
<li><p>le64: length</p></li>
<li><p>length bytes of actual data</p></li>
</ul>
</section>
<section id="zero-data">
<h3>Zero data<a class="headerlink" href="#zero-data" title="Permalink to this heading"></a></h3>
<ul class="simple">
<li><p>u8: ‘z’</p></li>
<li><p>le64: offset</p></li>
<li><p>le64: length</p></li>
</ul>
</section>
</section>
<section id="final-record">
<h2>Final Record<a class="headerlink" href="#final-record" title="Permalink to this heading"></a></h2>
<section id="end">
<h3>End<a class="headerlink" href="#end" title="Permalink to this heading"></a></h3>
<ul class="simple">
<li><p>u8: ‘e’</p></li>
</ul>
</section>
</section>
<section id="id1">
<h2>Header<a class="headerlink" href="#id1" title="Permalink to this heading"></a></h2>
<p>“rbd diff v2\n”</p>
</section>
<section id="id2">
<h2>Metadata records<a class="headerlink" href="#id2" title="Permalink to this heading"></a></h2>
<p>Every record has a one byte “tag” that identifies the record type,
followed by length of data, and then some other data.</p>
<p>Metadata records come in the first part of the image.  Order is not
important, as long as all the metadata records come before the data
records.</p>
<p>In v2, we have the following metadata in each section:
(1 Bytes) tag.
(8 Bytes) length.
(n Bytes) data.</p>
<p>In this way, we can skip the unrecognized tag.</p>
<section id="id3">
<h3>From snap<a class="headerlink" href="#id3" title="Permalink to this heading"></a></h3>
<ul class="simple">
<li><p>u8: ‘f’</p></li>
<li><p>le64: length of appending data (4 + length)</p></li>
<li><p>le32: snap name length</p></li>
<li><p>snap name</p></li>
</ul>
</section>
<section id="id4">
<h3>To snap<a class="headerlink" href="#id4" title="Permalink to this heading"></a></h3>
<ul class="simple">
<li><p>u8: ‘t’</p></li>
<li><p>le64: length of appending data (4 + length)</p></li>
<li><p>le32: snap name length</p></li>
<li><p>snap name</p></li>
</ul>
</section>
<section id="id5">
<h3>Size<a class="headerlink" href="#id5" title="Permalink to this heading"></a></h3>
<ul class="simple">
<li><p>u8: ‘s’</p></li>
<li><p>le64: length of appending data (8)</p></li>
<li><p>le64: (ending) image size</p></li>
</ul>
</section>
</section>
<section id="id6">
<h2>Data Records<a class="headerlink" href="#id6" title="Permalink to this heading"></a></h2>
<p>These records come in the second part of the sequence.</p>
<section id="id7">
<h3>Updated data<a class="headerlink" href="#id7" title="Permalink to this heading"></a></h3>
<ul class="simple">
<li><p>u8: ‘w’</p></li>
<li><p>le64: length of appending data (8 + 8 + length)</p></li>
<li><p>le64: offset</p></li>
<li><p>le64: length</p></li>
<li><p>length bytes of actual data</p></li>
</ul>
</section>
<section id="id8">
<h3>Zero data<a class="headerlink" href="#id8" title="Permalink to this heading"></a></h3>
<ul class="simple">
<li><p>u8: ‘z’</p></li>
<li><p>le64: length of appending data (8 + 8)</p></li>
<li><p>le64: offset</p></li>
<li><p>le64: length</p></li>
</ul>
</section>
</section>
<section id="id9">
<h2>Final Record<a class="headerlink" href="#id9" title="Permalink to this heading"></a></h2>
<section id="id10">
<h3>End<a class="headerlink" href="#id10" title="Permalink to this heading"></a></h3>
<ul class="simple">
<li><p>u8: ‘e’</p></li>
</ul>
</section>
</section>
</section>



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